The present invention generally relates to semiconductor processing and packaging, and in particular to a system and method for laser marking integrated circuit packages.
As the production rate of integrated circuit packages (hereinafter xe2x80x9cunitsxe2x80x9d) has increased, manufacturers have searched for ways to efficiently and reliably label their units with information such as company name, logo, part number, lot number, and serial number. While ink stamping has been used, laser marking, due to its higher speed, higher precision, and lower cost, has become the preferred method.
A number of laser marking systems have been described. Latta, Jr., U.S. Pat. No. 4,638,144 describes an automated system that laser marks parts loaded in lead frames, which can be stacked into magazines. The frames are carried along a conveyor. Arakawa et al., U.S. Pat. No. 6,031,202 also loads the parts into lead frames, but uses a rotatable index table to transport the frames to the laser marking area. Tsuruta, U.S. Pat. No. 5,357,077, describes a system where the parts are place in tubular holders on a conveyor. In these, and other laser marking systems, there is an unsatisfied need to obtain more consistent marking of all units.
A number of techniques have been proposed to improve marking consistency and to detect defectively marked parts. Liska, U.S. Pat. No. 5,629,484 describes using a sensor to detect the sound of the laser firing and stopping the production line when the laser does not fire as expected. Latta, Jr., U.S. Pat. No. 4,638,144 describes the use of electric eyes to detect when the leading edge of a part has entered the laser marking area and to determine when the flow of parts has been interrupted. However, parts are sometime incorrectly marked because they are not positioned correctly in the laser marking area and there remains an unsatisfied need for more reliable detection of incorrectly positioned parts.
The present invention provides a system and method for laser marking integrated circuit packages. The integrated circuit packages to be marked are positioned within trays. The trays have one or more pockets into which integrated circuit packages fit. If an integrated circuit package is not properly positioned within a tray pocket, at least a portion of the integrated circuit package sticks up. This condition is detected by an electric eye.
Trays with integrated circuit packages are placed on a conveyor and conveyed under an electric eye. The electric eye is positioned so that the beam of the eye is broken if, but only if, an integrated circuit package is improperly positioned within a tray pocket. If the beam is broken by an improperly positioned integrated circuit package, a controller can stop the conveyor, permitting the system or an operator to properly place the integrated circuit package within its pocket. If the beam is not broken, the conveyor takes the tray onward to a laser marking area where the integrated circuit packages within the tray can be correctly marked.
In one aspect, the invention provides a system for laser marking integrated circuit packages. The system includes a frame, a conveyor, trays for receiving integrated circuit packages, a laser marking device positioned to mark integrated circuit packages in pockets of trays on the conveyor, and an electric eye. The trays are sized to fit on the conveyor and having pockets into which the integrated circuit packages fit. The electric eye is positioned to scan over the conveyor in a line that is just above the plane in which integrated circuit packages will travel when they are fit within pockets of trays on the conveyor.
In another aspect the invention provides a system for laser marking integrated circuit packages, including a frame, a conveyor on the frame, a laser marking device on the frame, the laser marking device being positioned to mark integrated circuit packages traveling on the conveyor, an electric eye mounted on the frame and positioned to scan along a line passing over the conveyor, and a controller operatively linked to the electric eye and the conveyor, wherein the controller is configured to stop the conveyor when an object breaks the line scanned by the electric eye.
In another aspect, the invention provides a system for labeling semiconductor devices, including, a body, a carrying device attached to the body, a laser attached to the body and positioned to label semiconductor devices brought to the laser by the carrying device, a photo-electric sensor attached to the body, above and to one side of the carrying device, a light source positioned above and to the opposite side of the carrying device and shining on the photo-electric sensor, and a logic circuit operatively linked to the photo-electric sensor and the carrying device, wherein the logic circuit initiates an action whenever light from the light source ceases to shine on the photo-electric sensor.
In a further aspect, the invention provides a system for laser marking integrated circuit packages including means for holding integrated circuit packages, means for detecting whether the integrated circuit packages are properly held by the holding means, means for transporting the held integrated circuit packages to a laser marking area, means for positioning the held integrated circuit packages within the laser marking area; and laser marking means within the marking area.
Another aspect of the invention provides a method of laser marking integrated circuit packages, including the steps of loading the integrated circuit packages into a tray having pockets into which the integrated circuit packages fit, putting the tray on a conveyor, either before or after the loading step, conveying the tray under an electric eye that scans over the tray for integrated circuit packages that are not properly seated within the pockets, and laser marking the integrated circuit packages if all the integrated circuit packages are properly seated within tray pockets.